Moscow Nights ============= I have decided to try one of my Elektronika MK-90 [1] portable computers. For a long time I had one special item in my "todo.txt" file: ---------------------------- (D) +mk90 @test @code Try to play "Moscow Nights" BASIC example ---------------------------- As you may know, the Elektronika MK-90 is a USSR portable computer which used a PDP-11 CPU clone. It has a liquid-crystal screen (120x64), a full keyboard (with calculator-style keys), some 16 kB of RAM (but just about 10 kB available for user) and a ROM of 32kB (the BASIC was stored here) and two clots for "memory cards" (16kB each - there was no another size but it is said that the card controller can support memory chips up to 64kB). The display can show 40x8 characters and also some graphics (black and white only, of course). And there is also a communication port (the only known use is to connect to a very experimental Elektronika MK-92 dock with integrated plotter and with the tape recorder connector). The important thing is that the device has also a very simple beeper which can be used to produce some noise. So, it is a cute device which can run BASIC. It is a clone of an old version of the DEC PDP-11 BASIC [2] with some commands added and some others removed. I even have an original printed manual with sample programs. One of them is also a program which plays the soviet "Moscow Nights" melody with use of the beeper (via the PLAY command). I always wanted to try this one bud I never found time to code that. So this task was one of the long-standing in my "todo.txt". At January 1 I decided to code the program. It has only about 10 lines but half of them is filled with data for the PLAY command. Surprisingly, it worked... The result can be found on my Phlog page. IT is not pleasant but it somewhat resembles the melody... It was recorded with use of a simple microphone and the IRIS Indigo. If you are curious how the MK-90 works: the keyboard is not nice (similar to calculators or to the HP 2000LX keyboard but its quality is lower) and the screen font is big (and thus ugly). But shortcuts for most of BASIC commands are available on the keyboard (there was ever a transparent keyboard overlay available to have them on hand). The bad thing is that there is no BASIC command to write data/files to storage devices (and also no command to read such data). Interactive input is of course available and there is also the DATA statement. The device has also some commands to save, read, edit, delete and copy files (but the files are expected to be BASIC ones, with number at the beginning of each line). It is good to remember that MK-90 was not a finished product: only some 1500 pieces were produced, the BASIC 2.0 was only available on a data card (there is probably no actual MK-90 with the BASIC 2.0 in the ROM) and most of expected add-ons were made. For example, the device has commands to print on a printer but there is probably no such printer. The only know thing is the MK-92 dock which requires to use memory card with an updated BASIC (the 2.0) and it is very rare. Anyway, it is one of a few portable PDP-11 clones (the Elektronika MK-85 is even smaller - it's a calculator with the PDP-11 CPU). References: [1] http://www.pisi.com.pl/piotr433/index.htm#mk90 [2] http://bitsavers.trailing-edge.com/pdf/dec/pdp11/basic/DEC-11-AJPB-D_PDP-11_BASIC_Programming_Manual_Dec70.pdf [3] gopher://gopherpedia.com:70/0/Moscow%20Nights